Adsorption behaviors for clathrate hydrates of CO2 with mixed gases

Abstract

Here, the preference and adsorption capacities of guest molecules in the sI and sII hydrate of water cages when CO2 + H2S, CO2 + SO2 and CO2 + N2O gas mixture form hydrates are simulated by using grand canonical Monte Carlo and molecular dynamics hybrid simulations method. The results indicate that SO2 prefers to occupy large cages, H2S prefers small cages for CO2 + H2S and CO2 + SO2 and N2O exhibits little preference between small or large or cages of CO2 + N2O sI hydrates, respectively. The abundance ratio shows hydrate can effectively achieve the separation of flue gases. Moreover, the thermodynamics calculation results show that the impurity gases H2S, SO2 and N2O favors the formation of CO2 hydrate. The stability CO2 + H2S, CO2 + SO2 and CO2 + N2O sI hydrates is higher compared to the stability of sII hydrates. The phase equilibrium analysis provides clear evidence that enclathration of H2S and SO2 molecules into the water cages of the hydrate structure plays a crucial role in stabilizing the hydrate lattices. The findings of this study suggest that removal of certain flue gas impurities is not required during the replacement of CH4 in hydrate form with the CO2 gas. The current investigation provides theoretical background for executing replacement of CH4 in hydrate form with the CO2 gas.